Add general Rack::BadRequest. (#2019)

Used to communicate a class of exceptions that represent 400 Bad Request
semantics.

CHANGELOG.md

@@ -8,6 +8,10 @@ All notable changes to this project will be documented in this file. For info on
 
 - `rack.input` is now optional. ([#1997](https://github.com/rack/rack/pull/1997), [@ioquatix])
 
+### Changed
+
+- Improved handling of multipart requests. `rack.input` is now optional, and if missing, will raise an error which includes `module Rack::BadRequest`. Several other exceptions also include this module. ([#1997](https://github.com/rack/rack/pull/1997), [@ioquatix])
+
 ## [3.0.3] - 2022-12-07
 
 ### Fixed

lib/rack.rb

@@ -15,6 +15,7 @@
 require_relative 'rack/constants'
 
 module Rack
+  autoload :BadRequest, "rack/bad_request"
   autoload :Builder, "rack/builder"
   autoload :BodyProxy, "rack/body_proxy"
   autoload :Cascade, "rack/cascade"

lib/rack/bad_request.rb

@@ -0,0 +1,6 @@
+module Rack
+  # Represents a 400 Bad Request error when input data fails to meet the
+  # requirements.
+  module BadRequest
+  end
+end

lib/rack/multipart.rb

@@ -6,6 +6,8 @@
 require_relative 'multipart/parser'
 require_relative 'multipart/generator'
 
+require_relative 'bad_request'
+
 module Rack
   # A multipart form data parser, adapted from IOWA.
   #
@@ -14,6 +16,7 @@ module Multipart
     MULTIPART_BOUNDARY = "AaB03x"
 
     class MissingInputError < StandardError
+      include BadRequest
     end
 
     class << self

lib/rack/multipart/parser.rb

@@ -3,18 +3,28 @@
 require 'strscan'
 
 require_relative '../utils'
+require_relative '../bad_request'
 
 module Rack
   module Multipart
-    class MultipartPartLimitError < Errno::EMFILE; end
+    class MultipartPartLimitError < Errno::EMFILE
+      include BadRequest
+    end
 
     # Use specific error class when parsing multipart request
     # that ends early.
-    class EmptyContentError < ::EOFError; end
+    class EmptyContentError < ::EOFError
+      include BadRequest
+    end
 
     # Base class for multipart exceptions that do not subclass from
     # other exception classes for backwards compatibility.
-    class Error < StandardError; end
+    class BoundaryTooLongError < StandardError
+      include BadRequest
+    end
+
+    # Prefer to use the BoundaryTooLongError class or Rack::BadRequest.
+    Error = BoundaryTooLongError
 
     EOL = "\r\n"
     MULTIPART = %r|\Amultipart/.*boundary=\"?([^\";,]+)\"?|ni
@@ -96,7 +106,7 @@ def self.parse(io, content_length, content_type, tmpfile, bufsize, qp)
         if boundary.length > 70
           # RFC 1521 Section 7.2.1 imposes a 70 character maximum for the boundary.
           # Most clients use no more than 55 characters.
-          raise Error, "multipart boundary size too large (#{boundary.length} characters)"
+          raise BoundaryTooLongError, "multipart boundary size too large (#{boundary.length} characters)"
         end
 
         io = BoundedIO.new(io, content_length) if content_length

lib/rack/query_parser.rb

@@ -1,22 +1,30 @@
 # frozen_string_literal: true
 
+require_relative 'bad_request'
+
 module Rack
   class QueryParser
     DEFAULT_SEP = /[&] */n
     COMMON_SEP = { ";" => /[;] */n, ";," => /[;,] */n, "&" => /[&] */n }
 
     # ParameterTypeError is the error that is raised when incoming structural
     # parameters (parsed by parse_nested_query) contain conflicting types.
-    class ParameterTypeError < TypeError; end
+    class ParameterTypeError < TypeError
+      include BadRequest
+    end
 
     # InvalidParameterError is the error that is raised when incoming structural
     # parameters (parsed by parse_nested_query) contain invalid format or byte
     # sequence.
-    class InvalidParameterError < ArgumentError; end
+    class InvalidParameterError < ArgumentError
+      include BadRequest
+    end
 
     # ParamsTooDeepError is the error that is raised when params are recursively
     # nested over the specified limit.
-    class ParamsTooDeepError < RangeError; end
+    class ParamsTooDeepError < RangeError
+      include BadRequest
+    end
 
     def self.make_default(param_depth_limit)
       new Params, param_depth_limit

test/spec_multipart.rb

@@ -38,7 +38,7 @@ def multipart_file(name)
     env = Rack::MockRequest.env_for("/", multipart_fixture(:content_type_and_no_filename, "A"*71))
     lambda {
       Rack::Multipart.parse_multipart(env)
-    }.must_raise Rack::Multipart::Error
+    }.must_raise Rack::Multipart::BoundaryTooLongError
   end
 
   it "raises a bad request exception if no body is given but content type indicates a multipart body" do